PCI Express x16 graphics card in a PCIe x16 slot?

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I thought PCIe was superceding PCIX But I have 2 PCIe x 1 slots on my motherboard, 3 ordinary PCI slots and one which is

PCIe cards can always operate in PCIe slots with the same or more lanes than the card For example, an x8 card can operate in a slot with x8, x16, or x32 lanes  IPCIE16XD11 is Multiple SFF-8654 x4 to PCIe x16 Slot Expansion with Broadcom MegaRAID 9560-16i, 9560-8i, 9580-8i8e, 9500-16i, 9500-8i,

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